In recent times, it has been eagerly desired in the photographic industry to shorten access time. Thus, there has been a keen desire to develop a silver halide photographic material suitable for ultrarapid processing, particularly a silver halide emulsion for use in the preparation thereof.
Silver halides comprising silver bromide as the main component which have heretofore been mainly used are fundamentally unfavorable for rapid processing because the bromine ions released during development are development inhibiting. For ultrarapid processing, silver halides comprising silver chloride as the main component may be preferably used.
When the silver chloride content of the silver halide grains is increased, the water solubility of the grains is also increased, making it possible to develop and fix the light-sensitive material in a shorter period of time. Thus, a silver halide emulsion suitable for ultrarapid processing can be obtained.
However, silver halide grains having a high silver chloride content (hereinafter referred to as "high silver chloride content grains") are disadvantageous in that they normally can easily become 100 plane cubic grains which can be fast developed but can easily be fogged and exhibit a low sensitivity.
Further, the inherent absorption range of high silver chloride content grains is in a short wavelength range. In order to make the high silver chloride content grains absorb visible light and/or infrared radiation in a longer wavelength range and render the high silver chloride content grains sensitive also to the wavelength range, it is necessary to subject the high silver chloride content grains to spectral sensitization. However, even if spectrally sensitized with a compound commonly applied to emulsions comprising silver bromide as a main component, a silver chloride emulsion having a silver chloride content of 80 mol % or more normally exhibits poor absorption and remarkably poor spectral sensitizability. This is even more true when the silver chloride content is 95 mol % or more. Such compounds for spectral sensitization are normally methine dyes. In particular, cyanine dyes which provide emulsions having silver bromide as a main component with an extremely good spectral sensitizability have such a tendency. Among cyanine dyes, many compounds which form J-aggregates and provide so-called J-band sensitization in an emulsion comprising silver bromide as a main component to give a high spectral sensitivity have been recognized. This J-band sensitization is an essential technique for giving a high trapping of light of a specific wavelength (such as laser light) or for providing a light-sensitive material or color light-sensitive material sensitized to light of a specific wavelength range. However, compared to grains comprising silver bromide as a main component, high silver chloride content grains ca barely form such J aggregates and thus cannot benefit from J-band sensitization.
Moreover, high silver chloride content grains can easily become cubic grains, and an elaborate technique is needed to obtain grains other than cubic grains such as regular grain, e.g., octahedron having 111 plane and tetrdecahedron and tabular grains from high silver chloride content grains. In order to obtain such grains, modifiers for the growth of high silver chloride content grains are often used. For example, F. H. Claes et al teach in "Crystal Habit Modification of AgCl by Impurities Determining the Solvation", The Journal of Photographic Science, Vol. 21, pp. 39-50, 1973, and "Influence of the Habit of Silver Halide Crystals on the Absorption Spectra of Adsorbed Sensitizing", The Journal of Photographic Science, Vol. 21, pp. 85-92, 1973, the formation of silver chloride crystals having 110 plane and 111 plane with various grain growth modifiers such as purine derivatives and thiourea derivatives. F. H. Claes et al reported that J-band can be easily developed on a 100 plane and M- and D-band can be easily developed on 110 and 111 planes. JP-B-55-42737 (the term "JP-B" as used herein means an "examined Japanese patent publication") discloses the formation of dodecahedral silver chloride grains having a 110 plane with imidazole derivatives. U.S. Pat. No. 4,400,463 discloses the formation of tabular silver chloride grains having 111 plane as a main plane with adenine and poly(3-thiapentylmethacrylate)-co-acrylate-co-sodium 2-methacryloyloxyethyl-1-sulfonate. U.S. Pat. No. 4,801,523 discloses the formation of octahedral and tabular silver chloride grains having 111 plane with adenine derivatives. JP-A-62-218959, JP-A-63-213836, and JP-A-63-218938 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") disclose the formation of tabular silver chloride grains with thiourea derivatives. U.S. Pat. No. 4,225,666 discloses the formation of octahedral silver chloride grains having a 111 plane with merocyanine dyes. However, the silver chloride grains formed with such grain growth modifiers have a small amount of modifiers left on the surface thereof, and these modifiers strongly inhibit the adsorption of the spectral sensitizer which must be used to provide spectral sensitization, providing only a low spectral sensitivity or making the grains extremely foggable. Further, if a specific merocyanine dye is used as modifier, it causes spectral sensitization, providing sensitization in an unnecessary wavelength range and inhibiting sensitization in the desired wavelength range with a spectral sensitizing dye. The various disadvantages disable the silver halide grains used for silver halide light-sensitive materials.
One of the inventors discloses in JP-A-2-000032 that octahedral and tabular silver chloride grains having a 111 plane free from these disadvantages can be formed with bispyridinium salt derivatives as silver chloride grain growth modifiers. These modifiers can be easily removed after the formation of the grains. Therefore, the above cited invention is an excellent approach by which octahedral and tabular silver chloride grains having a 111 plane and having no modifiers left thereon can be obtained. Unlike cubic grains having a 100 plane, these grains can be easily subjected to chemical sensitization such as gold and sulfur sensitization without being fogged to provide a high sensitivity silver chloride emulsion. However, as taught by F. H. Claes in the above cited references, even if no silver chloride grain growth modifiers remain, high silver chloride content grains having a 111 plane barely form J-aggregates and exhibit a remarkably poor adsorption of cyanine dyes which are extremely important for the production of silver halide light-sensitive materials as compared to silver halide grains comprising silver bromide as a main component and cubic silver chloride grains having a 100 plane, imposing great restrtictions on spectral sensitization. Therefore, if an approach can be found which enables sufficient J-band spectral sensitization in a high silver chloride content emulsion having a 111 plane, a silver halide photographic emulsion and a silver halide light-sensitive material are obtained which exhibit a higher spectral sensitivity in a desired wavelength range and which can be subjected to ultrarapid processing.